Research from the Defence Studies Department, King's College London

British naval aviation in World War II: Escort Carriers

The Royal Navy pioneered the use of air power at sea, from bases ashore and from aircraft carriers, during the First World War. It lost this lead during the interwar period due to a range of factors including limited spending on defence and an unclear national strategy, exacerbated by the Navy losing control of its air arm to the newly independent Royal Air Force – which both insisted that it should control all air power and also attached a very low priority to maritime or naval air power. The Admiralty also wrongly believed that it had mastered the threat from submarines and was slow to fully appreciate the potential of aircraft in attacking warships, either as a threat that needed to be countered or as an asset that could be exploited. The return of the Fleet Air Arm to naval control shortly before the outbreak of war helped, but the Royal Navy began the conflict far short of the naval air power it would need to fulfil its roles in national and allied strategy. Efforts to build up its strength had to compete for resources with all of the other pressing needs, which not only included land and air forces, but other priorities at sea including escorts and merchant ships. The result was a strikingly imaginative and innovative approach, which saw a profusion in the ways of providing air power at sea, prefiguring the wide range of air-capable warships in service today.

There was a desperate need for more fleet carriers, that is, those capable of operating large numbers of the most modern aircraft, suitable for the most demanding operations against the enemy’s heavy warships or shore-based air forces. New fleet carriers would take time to build so the Navy began n parallel to construct ‘light fleet carriers’. While not as capable as their larger siblings, this ‘makeshift supplement’ could, it was hoped, be put into service more quickly and could play a valuable role in supporting the fleet. Yet hopes that the light fleet carriers could be made available rapidly were dashed; there was no point in having carriers that were incapable of operating modern aircraft and the rapid advances in aircraft capability forced ship designs to evolve. The light fleets would therefore take more time to complete. They then provided valuable service (and, indeed, went on to form an important element of post-war naval aviation both in the Royal Navy – in which they distinguished themselves in the Korean War, the Suez conflict and even, in the case of HMS Hermes, in the Falklands War – and in other navies to which some were transferred) but in the meantime, other solutions were needed.

The key to the approach taken was to split the tasks of naval aviation. The more demanding roles required an ability to take on front-line enemy aircraft or warships fitted with powerful anti-aircraft armament. This was the role of the fleet and light fleet carriers. Yet there was also a desperate need for air power in the protection of merchant shipping against the threat posed by enemy U-boats and land-based strike aircraft (both of which benefitted from bases in occupied France and Norway, transforming the threat posed by Germany in comparison to the First World War). Air power had a central role to play in this struggle, both land-based (when Coastal Command could prise a few crumbs from a table dominated by the insatiable appetite for long-range aircraft of Bomber Command) and sea-based, particularly in the mid-Atlantic air gap. Aircraft conducting these roles, and the carriers from which they operated, would not face the same threat as those operating with the fleet; less modern aircraft, in smaller numbers would suffice but would need many platforms.

The Navy rushed into service 35 Catapult-Armed Merchant (CAM) ships, each of which had a single fighter aircraft. These vessels lacked a flight deck so they were a one-shot weapon, with the embarked fighter launching to shoot down a shadowing enemy reconnaissance aircraft which could otherwise report the location of the convoy. The pilot would then ditch in the sea in the hope of being picked up by one of the ships he had just protected. It also commissioned 19 Merchant Aircraft Carriers, or MAC ships. These countered the objection that converting merchant ships into carriers cost Britain precious cargo tonnage; they were large grain ships or tankers fitted with a flight deck, allowing them both to launch and recover aircraft for the loss of only a small proportion of their carrying capacity.

These innovations were only part of the solution, an interim measure while the main effort came into play. The Admiralty had considered ‘auxiliary carriers’ in the interwar period, and now pressed ahead to introduce them – a process that was painfully slow due largely to the competing pressures on Allied shipyards. The escort carriers, as they became known (also called ‘Woolworth’ or ‘jeep’ carriers) were either converted merchant ships or purpose-built but relatively simple ships. They were better equipped than the CAM and MAC ships with full-length flight decks, catapults and arrestor wires, most with hangars too, but operated fewer aircraft, usually less capable models, than the fleet carriers – typically a dozen as against around 50. For convoy protection, the complement was mainly Torpedo-Bomber-Reconnaissance aircraft for anti-submarine uses but they also operated a few fighters against the threat of long-range reconnaissance or strike aircraft. Their main role was in directly supporting shipping, either accompanying convoys or, as more became available, operating with detached Support Groups.

The first real test of the escort carrier concept was HMS Audacity – a captured German merchant ship put to good use – which commissioned in September 1941. She successfully protected a number of convoys, her aircraft shooting down several German aircraft and contributing to the destruction of a U-boat. By the time she was torpedoed and sunk in December of the same year, the idea was entirely vindicated. During the war, Britain would commission no fewer than 44 escort carriers – the US Navy also made extensive use of them.

The concept was so successful that their uses proliferated and specialised versions emerged. Escort carriers operating with the Russian convoys had to run the gauntlet of heavy land-based air opposition, so they were modified to carry more advanced fighters. The rapidly proven utility of carrier-based air power in supporting amphibious operations gave rise to the ‘assault carriers’, designed to operate modern fighter-bombers in support of amphibious operations – typically they would provide direct support to the landings while the fleet carriers provided cover against enemy forces.

These further innovations gave the escort carriers a wider range of potential roles – which had a positive side, in providing more air support for key activities (including working directly with the fleet, in support of fleet and light fleet carriers), but also a negative one in reducing the number available for trade protection. The escort carriers therefore helped to ease the problem caused by stretched resources and competing priorities but could not resolve it.

My research on British naval air power at the time of D-Day revealed a fascinating picture of the range of tasks conducted by these versatile ships. On 6 June 1944, there were 30 escort carriers in service in the Royal Navy. One was operating with the Home Fleet off Norway, providing cover for the Normandy landings. Three were deployed in the South-West Approaches conducting anti-submarine patrols to protect the landing areas. Five were preparing for subsequent amphibious operations in the Mediterranean. Nine were protecting merchant shipping (two with the Russia convoys, the rest in the Atlantic). Five were either serving with or deploying to the Eastern Fleet. Three, along with several others that were working up but not yet in service, were ferrying aircraft between theatres, lending the strategic mobility of naval power to their land-based counterparts. Two more were repairing, one was being used to train pilots in deck landing and one for trials of new aircraft.

They could also switch rapidly between roles. One example is the activities of HMS Emperor in late spring and summer 1944. In April and May she was attached to the Home Fleet, off Norway, participating in the successful attack on Tirpitz, attacking German shipping and targets ashore, and contributing to the Allied deception campaign. On 6 June, she was one of the escort carriers providing air cover for the forces countering U-boats in the South-West Approaches. She then deployed to the Mediterranean to support Allied amphibious operations in July and August.

The escort carriers deserve to be better known than they are, and not only because of their value in a whole range of naval roles during the war. They also represented a pragmatic and innovative solution to a pressing problem, namely how to exploit the huge potential of air power at sea in circumstances where resources were limited. A similar approach can be seen in the embrace by the post-war Royal Navy of the helicopter, the commando carrier and the short/vertical take-off and landing aircraft. Moreover, the escort carriers provide a counter-example to the charge sometimes levelled against armed forces in general and navies in particular, that they always opt for the biggest, best, most ‘gold-plated’ solution.

Image: HMS EMPEROR at sea with other escort carriers, this was the night before the Fleet Air Arm raid on the German Battleship TIRPITZ (2 April 1944), via the Imperial War Museum.